Dread Necromancer is cool but if you wanted to go with a specialist necromancer Wizard and went down the Abjurant Champion Route you wouldn't need to worry about armor at all. You could just buff yourself and have a great AC. However, that's kinda optimizing and if you're in it just for the flavor I'd say go with Dread Necromancer and use some of the advice people have already stated. Just keep in mind that you will want something item or spell wise to counteract the loss of movement speed due to your armor. There's lots of ways around this.